Method for relieving center segregation of super-thick plate blank high-carbon steel

Abstract

The invention provides a method for relieving center segregation of super-thick plate blank high-carbon steel. The method is used for conducting reduction treatment on the super-thick plate blank and comprises the following steps of that 1) reduction treatment is conducted on a two-phase region, the solid fraction of a casting blank is calculated firstly according to a formula fs=(Tl-T1) / (T1-TS), and then the reduction amount is determined according to the solid fraction; and 2) reduction treatment is conducted on a solid-phase region, the temperature difference at the reduction position of the casting blank is calculated firstly according to a formula dt=TS-T2, and then the reduction amount is determined according to the temperature difference, wherein reduction is not conducted when dt is greater than 60 DEG C, and the reduction amount is 1.5-4.5mm when dt is smaller than or equal to 60 DEG C. The method has the advantages of being simple in process, easy to implement and capable of being implemented by utilizing existing equipment. By adopting the scheme, the center segregation ratings of 1 / 4, 1 / 2 and 3 / 4 positions of the width of the casting blank are all qualified, and the internal quality of the super-thick plate blank high-carbon steel is obviously improved.

Description

technical field [0001] The invention belongs to the technical field of steelmaking and continuous casting, and in particular provides a method for improving central segregation of ultra-thick slab high-carbon steel aimed at the production practice of continuous casting of ultra-thick slabs with a thickness exceeding 450mm. Background technique [0002] Usually, people classify slabs with a thickness specification > 450mm as ultra-thick slabs, and steels with a carbon content in the range of 0.25%≤C (wt%) are classified as high-carbon steels. During the solidification process of slab continuous casting, there are two defects that cannot be eliminated. One is the unavoidable center segregation due to fractional crystallization, and the other is the W-shaped solidification end during the solidification process of the slab. Regarding the formation causes and hazards of slab continuous casting center segregation, many domestic and foreign literatures have elaborated in detail:...

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Problems solved by technology

[0003] The invention patent with the patent number CN201811567253.1 discloses a dynamic secondary cooling and light reduction control system for slabs. amount and reduction interval, dynamically optimize the roll gap value of each reduction segment, and achieve the purpose of reducing slab center segregation and center porosity defects.” This patent only implements light reduction in the two-phase area, and does not consider slab continuous casting The solidification characteristics of the W-shaped liquid core and its influence on the center segregation of the slab, while the W-shaped solidification end of the ultra-thick slab is more prominent, and a specific center segregation control technology must be adopted for the final solidification area

[0004] During the first 480mm straight-arc ultra-thick slab continuous casting practice in China, it was found that the central segregation and W-shaped solidification end of the ultra-thick slab were more serious than those of the medium-thick slab, and the conventional light reduction technology could not be effective Improve the internal quality of ultra-thick slabs. At present, there is no reference experience for high-quality ultra-thick slabs with a thickness of 480mm in China. We can only continue to explore, optimize and innovate in production practice

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